Ecojustice lawyers representing the three groups filed the lawsuit at the federal court level, saying that the Joint Review Panel's (JRP) final report on the pipeline is based on insufficient evidence and does not satisfy the legislated requirements of the environmental assessment process.

"The JRP did not have enough evidence to support its conclusion that the Northern Gateway pipeline would not have significant adverse effects on certain aspects of the environment," said Karen Campbell, Ecojustice staff lawyer.

The panel, a joint effort of the National Energy Board and the Canadian Environmental Assessment Agency, held an 18-month review of the proposed $6.3 million Enbridge pipeline, which would ship 520,000 barrels per day of diluted oilsands bitumen to the B.C. coast for export on tankers.

The three groups behind the lawsuit were participants in the review process.

Campbell said that the panel made its recommendation "despite known gaps in the evidence, particularly missing information about the risk of geohazards along the pipeline route and what happens to diluted bitumen when it is spilled in the marine environment."

For example, the panel's conclusion that diluted bitumen is unlikely to sink in an ocean environment was refuted by a federal report released last week. This suggests that potential spills could have more serious environmental impacts and be more difficult to clean up than the panel's report makes evident.

Karen Wristen, executive director of Living Oceans Society, said that they "have no choice but to go to court and challenge the JRP's final report."

"The panel's recommendation was made without considering important evidence that highlights the threat Northern Gateway poses to the B.C. Coast," Wristen said.

The panel also failed to consider the final recovery strategy for humpback whales or identify mitigation measures to reduce the impacts on caribou, as required by sec. 79(2) of the Species at Risk Act.

"The proposed tanker route travels directly through humpback whale critical habitat identified in the recovery strategy. Yet the panel refused to consider this potential conflict when making its recommendation," said Dr. Paul Paquet, senior scientist at Raincoast Conservation Foundation.

Paquet said that "the panel's failure to consider the project's likely adverse impact on the whales makes no sense," considering that "the federal government will be required to legally protect the humpbacks and their habitat beginning in April."

Although the panel's final report concluded that 35 per cent of the Northern Gateway's economic benefit would come from upstream oilsands development, it did not address the environmental impacts associated with oilsands development, despite a clear request to do so.

Nikki Skuce, senior energy campaigner with ForestEthics Advocacy, said that the panel "cannot consider the so-called economic benefits of oilsands expansion tied to this pipeline but ignore the adverse impacts that expansion will have on climate change, endangered wildlife and ecosystems."

"The environmental assessment process is supposed to consider both sides of the coin, and in this instance the panel failed," Skuce said.

The panel's environmental assessment found the oil tanker and pipeline project was unlikely to have adverse environmental effects, aside from cumulative impacts on some grizzly bear and caribou populations. Campbell said this conclusion was reached "without considering all the necessary and available science."

Campbell added that the report "only tells part of the story, and we are asking the court to ensure that this flawed report doesn't stand as the final word on whether Northern Gateway is in the national interest."

The lawsuit seeks a federal court ruling to prevent the government from relying on the flawed report to approve Northern Gateway.

A spokeswoman for Natural Resources Minister Joe Oliver said the government would not comment on the lawsuit, reports the Globe and Mail.

"As the minister said before, we will thoroughly review the report, consult with affected First Nations, and then make our decision," said Melissa Lantsman, Oliver's director of communications. "Our government will continue to take action to improve the transportation safety of energy products across Canada."

Cabinet is set to make a decision based on the panel's recommendation in the following six months. Under the new environmental assessment framework forced through in the 2012 spring omnibus budget, cabinet has final decision-making power over Northern Gateway, bound by the 209 conditions laid out in the panel's report.